Method of making a tubular article



Oct. 11, 1938.- T. A.` GRAHAM 2l32,565

METHOD OF MAKING TUBULAR ARTICLE Filed May 13, 1937 2 Sheets-Sheet 2 F'IEA'.

Patented Oct. 11, `1938 METHOD F A TUBULAR ARTICLE Thomas A. Graham, San Francisco, Calif., assignor to National Tube Company, a corporation of New Jersey Application May 13, 1937, Serial No. 142,455

I6 Claims.

'I'his invention particularly relates to `af method of making a tubular article that is provided with an outwardly extending drip lip or fin in the circumference thereof.

An object of this invention is to provide a practical, eflicient method of making tubular articles of this class.

The above and further objects will become apparent by referring to the following description and the accompanying drawings in which:

Figure l is a longitudinal sectional elevation of one embodiment of apparatus for performing one of the steps of my invention;

Figure 2 is a transverse sectional elevation on line II-II of Figure v1;

Figure 3 is a transverse. sectional elevation on line III- III of Figure 1;

Figure 4 is a longitudinal sectional elevation of one embodiment of apparatus for `performing a further step of my invention;

Figure 5 is a transverse sectional elevation on line V-V of Figure 4; and, s

Figure 6 is a transverse sectional elevation of the finished tubular article.

;, Referring more Aparticularlyvto the drawings the numeral 2 designates a ltubular blank or tube which preferably has previously been cold drawn to the equivalent round size desired in a heat transfer conduit ortubular article 4 `to be `made therefrom. The tube 2 can rbe drawn by they standard lead coated or other suitable method and ordinarily should have a Wall slightly thicker than that.A desired in the tubular articley 4,

l 4To form a drip lip or nn in` the wan of the tube 2, the tube 2 is preferably drawn through the pass formed by a 4die 6 and a mandrel 8.

The pass formed `by thedie `6 and the mandrel 8 is designed to fabricate an outwardly extending drip lip or fin l, which is substantially '40 V-shaped-insection, in the wall of the tube 2 and reduce the diameter thereof but keep the remainder of the tube 2 substantially round. The n ID preferably extends radially from the 'tube 2 and, as the tube 2 was positively held 45 when drawn through .the die 6 and the mandrel 8, the iin I0 is straight and longitudinally'` directed, as desired. Ordinarily the length of the periphery of the tube 2 is not changed when the tube is drawn over the mandrel 8. After. the

5o fin I0 is formed in the tube 2, the lead on the tube (if any) is removed and the tube is heat treated, straightened, cut and finished in the ordinary manner.

After the tube has been treated in the above 55 described manner a second tubular blank or tube (Clf 29-156) I2 is disposed therein by any suitable means. The tube I2 has preferably been drawn by the standard lead coated method to an outside diameter but slightly smaller, for example onev sixteenth of an inch, than the inside diameter 5 of the tube 2. Also, any lead on the tube I2 should be removed and the tube finished by a process similar to that given the tube 2. The tube I2 is provided witha smooth circular bore which is substantially the size desired in the 10 finished tubular article 4. Both tubes are preferably made from stainless steel, as it does not easily corrode and, in addition, is a goodv heat conductor.

To make the vtube I2 integral with the tube 1,5 2 and form the tubular article 4, an expandingmandrel I4 or other suitable means is drawn through the tube I2 while the tube 2 is held thereon. The mandrel I4 is adapted to expand the tube I2 until the outer surface thereof bears 20 upon and' preferably slightly expands the outer tube 2. 4Lubricating means, such as aluminum paint, is supplied to the mandrel I4 during the drawing operation.` The inner tube I2 must be expanded a sufficient amount so that its outer` 26 surface bears `upon all of the inside surface of the outer tube 2 except for the portion thereof forming the fin I0. As the tubes are in tight contacta good heat transfer relationship is established therebetween. The expanding man- 30 drel I4 is adaptedto leave a smooth circular bore in the -tube I2 after it has been drawn therethrough. The surface ofthe louter'tube4 2 may be polished, `if desired, and the tubes eut or finished in 35 any given manner to prepare the tubular article 4 for use. i

The tubulararticle 4 isfparticularly adapted Aforusein liquid coolers or regenerators or chemical apparatus in'iwhich cleanliness is required. 40

"The surfaces'uof thefinlshed article are not effected by ordinary corroding agents but, if any impurities do collect or remain thereon, both the inner and outer surfaces of the? tubular article 4 are easily cleaned.

In use, a plurality of the tubular articles 4 are to be horizontally positioned 'and placed irn- I mediately above or below one another in the same verticalplane. The fins I0 must extend downwardly from the tubular articles 4. Then vany liquid that is permitted to flow onto the uppermost one of the tubular articles 4 flows over the maximum amount of surface area of each tubular article as the liquid clings to the circumference thereof until led to flow therefrom by 5K the top of the tubular article immediately below that n so that, due to the maximum contact obtained, a maximum amount of heat can be transferred between the inner and outer surfaces of the tubular articles l. Of course, a iluid is contained in the bores of the tubular articles 4 when a liquid is permitted to flow over the outer surfaces of the tubular articles lf The tubular article l has been tested and found to readily and eiiiciently exchange .heat between the inner and outer surfaces thereof. The liquid to be heated or cooled can be placed in contact with either surface of the tubular article l.

While I have shown and described one form of apparatusfor carrying out the steps of my method, it will be understood that I am not limited thereto, since various modifications thereof may be made without departing from the scope of my invention as defined by the following claims.;

I claim:

Y 1.' That method of manufacturing a heat transfer conduit having a smooth circular inner bore and a longitudinally extending drip lip or iin in i the circumference thereof which comprises forming a tube having a radially outwardly extending drip lip or iln in its wall extending longitudinally and continuously the length of the tube, the drip lip or n being substantially V-shaped in section,

disposing al second tube having an outside diameter but slightly smaller than the inside diameter of the first mentioned tube inthe bore of the first mentioned tube, and expanding the inner tube until the outer surface thereof bears upon and slightly expands the outer tube so as to slightly spread the V-shaped drip lip inKthe wall thereof Y. so that said inner tube is securely held within said outer tube and all of thesurface of the outer tube except for the portion thereof forming the drip 11p or fin being in tight heat transfer relation with the surface of the inner tube.

2; That method of manufacturing a heat transfer conduit having a smooth circular inner bore and a longitudinally extending drip lip or iin in the circumference thereof which comprises forming a tube having substantially the equivalent round size desired in the heat transfer conduit, fabricating a radially directed outwardly extending drip lip or n in its wall extending longitudinally and continuously the length of thev'tube,

- eter but slightly smaller than the inside diameter of the iirst mentioned tube and a circular bore disposing a second tube having an outside diamof substantially the size desired in the nnished conduit in'the bore of therst mentioned tube,

and expanding the inner. tube until the outer surface thereof bears upon vand slightly expands the outer tube so as to slightly spread the outwardly extending drip lip in the wallthereof so` that said inner tube is securely held within said outer tube.

3. That method of manufacturing a heat transfer. conduit having a smooth circular inner bore fabricating a longitudinally and continuously directed radially outwardly extending drip lip or fin in the wall of the tube, the drip lip or iin -being substantially V-shaped in section, disposing a second tube having an outside diameter but slightly smaller than the inside diameter of the first mentioned tube and a circular bore of substantially the size desired in the'iinished conduit in the bore of the first mentioned tube, expanding the inner tube until the outer surface thereof bears upon and slightly expands -the outer tube so as to slightly spread the V-shaped drip lip in the wall thereof so that. said inner tube is'securely held within said outer tube and all of the surface lof the outer tube except for the portion thereof forming the drip lip or n being in tight heat transfer relation with the surface of the inner tube, and finishing the surface of the outer tube.

4. The method of making a tubular article which comprises forming a stainless steel tube by passing the tube between a mandrel and a die to form a radially outwardly projecting .rib-like drip-lip in its wall, extending longitudinally substantially the length of said tube for directing the flow of liquids therefrom, placing a second smaller stainless. steel tube within said first mentioned tube and passing a mandrel through said second mentioned tube to expand the same so that the entire outer surface of the last named tube is in close contact with the inner surface of the first named tube.

5. The method of making a tubular article which comprises providing an outer tube having `an outwardly projecting drip lip portion formed Vin the wall thereof, disposing a` second tube within said outer tube, and expanding said inner tube until it contacts the inner wall of said outer tube and slightly expands said outer tubevso as to slightly spread the outwardly projecting drip lip portion in the wall thereof so that saidY inner tube will be securely held within said outer tube.

6.. The method of making a tubular unit for use in liquid regeneratorsand the like which comprises forming a metallic outer tube with a radiallyoutwardly projecting rib-like drip lip portion in its wall extending longitudinally and continuously substantially the length thereof, disposing a second tube within said outer tube `after it is so formed, and drawing a mandrel through said inner tube to expand the same until it contacts the inner surface of the outer tube and slightly expands said outer tube so as to slightly spread the projecting rib-like drip lip portionin the wall thereof so that said inner tube is securely held within said outer tube and in close contact with substantially the entire inner surface of said outer tube.

THOMAS' A. GRAHAM. 

